This is a complete working implementation of adaptable priority
queues.  It consists of all the .java files that were given
to you for HW6, with the following improvements:

- The files are now divided up into three packages:

     container -- basic classes and interfaces such as Position,
                  that are useful for all containers.

		  (A container is a data structure that is
		  meant to contain other objects.  This course
		  is mostly about containers.)

     tree --    classes and interfaces needed for a heap tree.
                Makes use of the container package.

     pqueue --  adaptable priority queue classes.  Makes use of the
	        container and tree packages.
                 
- Accordingly, each Java file starts with a declaration of what
  package it's in, and what class names it would like to import from
  other packages.

- In addition to the .java files we gave you for HW6, there are also
  some .class files included in the pqueue package.  These are
  compiled (and obfuscated) versions of the pqueue-related Java files
  that YOU had to write for HW6.  So now you have everything you need
  to use adaptable priority queues.

  (We are not providing .java source for those files, in case someone
  is still working on HW6.)

- We've included the container.EqualityTester interface that you'll
  need for HW7.